It's a Pill

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Marilyn

Why can my cat get an antibiotic injection that lasts two weeks while we humans have to take pills several times every day?

—John Nelson, Lakewood, Colorado

Anyone who has tried to give a cat a pill understands the appeal! (The injections are available for dogs too.) But the drawbacks are too significant for humans. First, all drugs have side effects. If a patient reacts badly to a long-acting drug, he or she is stuck with it. By contrast, a short-acting drug clears the system quickly. Second, a drug that lasts, say, two weeks at full strength doesn’t simply disappear at that time. Instead, low levels stay in the system for a couple of months. This may foster antibiotic resistance.